On board many aircraft, the FMS (Flight Management System) fulfils, among other things, the function of predicting the progress of a flight plan, which involves predictions, at each point of this flight plan, of the times of passage and of the speeds, as well as of the fuel consumed. These predictions are, however, extremely dependent on the winds encountered and therefore on the modelling of these winds.
The wind database on board aircraft can be obtained from two potential sources: on the one hand, from meteorological stations on the ground providing a service that can cover the entire earth but often with a poor sampling (in space and time) with respect to the requirements of the FMS, and on the other hand, the onboard meteorological functions provided by the ISS system and involving a meteorological radar. The latter data have the advantage of being very well sampled, but are valid only in the immediate environment of the aircraft, and over a limited time horizon.
The diagram of FIG. 1 represents an example of wind measurements supplied by a meteorological station on the ground. In this figure, the directions and intensities of the wind are represented at a few points in space, and in the present case, at four points A, B, C and D only, which, as specified above, constitutes an excessively low spatial sampling.
The complementary nature of the information supplied by the two abovementioned sources does not, however, mitigate the weakness of the sampling in space and time of the winds when considering points distant from the aircraft.